Thread control for weft replenishing looms



March 10, 1953 R. G. TURNER THREAD CONTROL FOR WEFT REPLENISHING LOOMS Filed D60. 11, 1951 FIG.I3

INVENTOR RICHARD G. TURNER 'March 10, 1953 R. G. TURNER THREAD CONTROL FOR WEFT REPLENISHING LOOMS Filed D60. 11, 1951 ATTORNEY Patented Mar. 10, 1953 UNITED PATENT 11 C aims; 1

This invention relates to improvements in G011,- trol mechanism for the thread of the bobbin which is transferred into the depleted shuttle of a weft replenishing loom du ing a. loobbln changing operation. in a gi g looms mo e pa t cularly o the multicolor type generally employ a stationary a az e a g stacks of reserve bobbins th threads or weft ends of which lead to a thread holder. The bobbin chan i operation occurs a the lay is movin torwardly and the shuttle i picked approxima ly one quarter of a piols or.

rev l i n of the crank shaft thereafter when th lay is at or near its top center position, At the time of picking it is desirable to have the. thre of the freshly chan ed bobb n held by t e. hread holder in rear position favorabl for self-thread in of the shuttle when it is etched subsequent to replenishment. As the shuttle travels across he loom he thread from t e new bo bin sh uld p u er e .for of the ce er i g stop motion, but if the thread holder remains in rear position there is likelihood that the thread will be too far back to support the fork and the latter will cause unnecessary loom stoppage. To avoid this stoppage the thread holder should be returned to its forward position to move the thread under the fork, preferably priorto the end of the flight of the freshly replenished shuttle and when the lay is near its bottom center position.

Stationary magazines of the type already-mentioned generally employ a setting shaft which, on a replenishing beat of the loom, is rocked from its normal position to a transfer or set position while the lay is between its top and bottom center positions at a time more than one heat of the loom prior to the aforesaid bottom center posittion of the lay when the thread: holder should. he returned to its front posit-ion- ".I-he driving shaft of he loom which reciprocates the lay eomnk t s a rotation each beat of the loom and because. of its proximity of the thread holder it is desirable to have the forces for moving the holder derived from the crank shaft, b t the driving shaft com-- pletes a rotation in less, than. the aforesaid time,

In order to utilize forces derived from thecrank sh ft o m ve the thread. holder and utlhle the s tt ng s aft to in at the thread holder moving operation it is an imp rtant obj ct of the present invention to provid m ans wh reby an. indication given by the setting shaft when it roolre to set position can be stored until the. time arrives in the operation of the loom when a oneopigl; cycle of movements of the thread holder 'b started with assurance that it will be correctly 2. placed-tor shuttle threading When his time r tes mocha e ther ope ated or cont ol ed by an ao u tor d ven by the cr nk sha t h oolhe operative to elifo t movem nt of. he hr ad h lde fi s a. backwa d irec on and then a t rwarddirection,

It is a o ther object or t e inventi n to use an a tuator in: the. forms of a. cam o the top or halt to melt a corn lever c nnected to the th d h lder wh ch plvot dior tool; and-forth mov me The l ver normally out f alignment with the cam and. s associat d, with eeiliertt means n. whi h ner y is s ored by the set ing h rt the atter moves to ransfer pos tionv The com has h gh and low areas. and the cam e er w ll be mo ed la ally aga n a partof the com cor esponding o a high area by a oroederivedtir m. the etting sha t and t ansmitted through the resil ent means. The latter t en to move he ver int alig ment. with the oamrwhen a low a ea o the cam arrives under end ofv th l ver Thereafter the cam fieots the aforesaid hack and forth mov ments. of the th ead dersh set ing sha t generally urn d to no mal posi ion prior to c mpl t n o 'the mo ments of the thread holder and is not thereafter able to contr t e o n of e le er, It s a st ll further object or e i v nt to pr v de the cam lever with a flange or the like which will hold the lever inalignment with the cam after the setting shaft returns to normal positlon.

In order that the invention may he clearly understood, reference is made to the accompanying drawings which illustrate by way of example the embodiments of the invention and in which:

Fig, 1 is a side elevation of a Weft replenishing loom partly in section showing the invention applied thereto,

Fig. 2 an enlarged plan view looking inthe directionto f arrow?) 1- Fig. 3 is an enlarged front elevation looking in the direction of arrow 3, Fig. 2, partly in section, showing the unit on which the cam lever and parts associated with itare mounted,

Fig. 41s a horizontal section on lineiwil, Fig.3., showing the cam lever in two difierent. positions,

Fig; 5. is an enlarged rear elevation. looking the direction of arrow 54, Fig; Ltshowing; mrtoi the stationary magazine with; aforesaid set,- tin shaftin the norm l os ion thereot.

Fig. its a fragme ary side. elevation. 9 my loolsing. the direction ol arrow 5,

Figs. 7 and 8 are diagrammatic views showing the cam lever in two positions with respect to the cam,

Fig. 9 is a diagrammatic side elevation showing the manner in which the cam and cam lever operate to move the thread Fig. 10 is a diagrammatic plan view of the lay showing the latter in two positions,

Fig. 11 is a side elevation of the actuator cam, the driving shaft on which it is mounted being shown in section,

Fig. 12 is a side elevation of the cam shown in Fig. 11, and

Fig. 13 is a diagrammatic view of parts of the magazine as viewed from the center of the loom with the parts in the positions they occupy during a bobbin transferring operation.

Referring to Figs. 1, 5 and 13, the loom frame I supports a multicolor reserve bobbin magazine M which in the present instance is provided with four vertical stacks of reserve bobbins indicated at 2. The loom has a lay 3 provided 'with a shuttle box 4 which receives, one at a time, the several self-threading shuttles which are usedin the loom. One of theseshuttles S is indi'cated in Fig. 1. The lay has a bunter 5 to engage a latch 6 pivoted to a transferrer arm I which is normally in raised position as shown in Fig. 1. The lay is also provided with the usual center filling stop motion fork F, and shuttle picking mechanism indicated at P in Fig. 1 is provided to pick the shuttle when the lay is at or near its top center position.

The loom has a top or crank shaft l which .effects back and forth reciprocation of the lay y connectors one of which is shown at l l in Fig. 1. This shaft rotates once for each beat of the lay and turns the lay successively through front,

gears l3 and I4 connect to the shafts.

Referring more particularly to Figs. and 13,

the magazine is provided with a fixed stud 15 on n .which is pivoted a shuttle position detector It.

The magazine is also provided with a setting .shaft I! having an operating shelf l8 secured thereto normally in the raised position shown in Fig. 5.- This shaft I! is connected to the latch 6 by well-known mechanism not shown herein effective when the shaft rocks from the normal to the set position thereof, counter-clockwise in .Fig. 5, preparatory to a weft replenishing operation to lift the latch into the path of the hunter 5.

The magazine has a plurality of vertical slides one of which is shown at in Fig. 5 and these slides are provided with dogs 21 pivoted at their upper ends. In Fig. 5 the slide is shown in its normal down position, but when a bobbin changing operation has been called the slide corresponding to the depleted shuttle will be raised and as it is subsequently depressed its dog will engage the shelf l8 to rock the shaft I! to its transfer or set, position one effect of which is to move the shuttle position detector I 6 rearwardly, to the left inFig. 13. Motion of detector 16 is effected by means of a vertical rod 25 attached'at its upper end to an arm 21 secured to shaft 11. Movement of the setting shaft to its set position rocks the detector 16 in a clockwise direction as viewed in Fig. 13 so that the lower end 28 thereof moves rearwardly. This movement of the taut.

4 positions and movement of the detector 16 to its rearward detecting position will ordinarily occur while the lay is between its top and bottom center positions immediately before the front center position of the lay on which the replenishing operation occurs a. short time after the shuttle is picked from the opposite end of the loom from that shown in Fig. 1.

As the lay moves toward front center bunter 5 will engage the latch 6 to give the transferrer arm 1 a bobbin changing operation to replenish the shuttle S with a bobbin released from one or another of the stacks and designated herein at plenishing beat of the loom. If the shuttle should be misplaced the detector [6 is rocked back to its normal position to return shaft [1 to its normal position in time to permit the latch 6 to fall below the path of the hunter to cancel or revoke the bobbin changing operation.

The matter thus far described. operates in the usual manner and has beenset forth to provide an .understanding of the relation between the timing of the mechanisms of the ordinary stationary magazine loom and the invention as set forth hereinafter.

In carrying the invention into effect the weft ends or thre'adsW leading from the bobbins 2 in the magazine are attached to a thread holder member designated generally at H. When the previously mentioned bobbin B is transferred into the shuttle its thread, designated herein at W! will move with the bobbin but will remain attached to the thread holder. In the present instance this holder is of the geared type and has front and back gears 30 and 3|, respectively, between which the threads W extend and by which they are drawn away from the magazine and held The thread holder member includes an arm 32 having'a-hub 33 pivoted on one of the tie rods 34 of the magazine, thus permitting the member H to occupy either front or back position in the loom.- The hub 33 is limited as to its longitudinal position along the tie rod by collars 35.

A stop member 36 is held by set screws 3'! in angularly and longitudinally adjusted position on an extended end of the tie rod 34 and has front and back downwardly diverging arms 38 and 39 between the lower ends of which the thread holder supporting arm 32 extends. These diverging arms are provided with adjustable stop screws 40 to limit back and forth motion of arm 32.

A stand 45 is secured at 46 to a part 4! of the loom frame and has mounted therein a horizontal stud 48 which as shown herein is substantially parallel to the top or crank shaft 10. .The operator means for the thread holder is mounted-on this stud 4Band includes a cam lever designated generally at L. Lever L has a bearing 50 rockably mounted on the stud 48. A

: finger '5l onthe-bearing-passes' under a stop pin 52 fixed to stand 45 to limit counter-clockwise movement of the bearing and cam lever L as viewed in Fig. 1.

setting shaft-ll and the latch B'to their transfeg f- 'Ih'e bearing 50' has a vertica l stud 53 on which is pivoted a lever arm designated generally at 54.. A stop finger 55 on arm 54 engages the. stud 48 to limit rocking. movement of the arm 54 in a counter-clockwise direction as viewed in Fig. 4. As shown herein arm 54 includes a strip 56 of sheet metal fixed with respect to bearing 50 and extending horizontally forwardly- The front end of strip 56 carries a stud 5! on which is rotatably mounted a roll 58. A guide flange 59 on stud 51 is of larger diameter than roll 58 and serves a, purpose to be described.

A leaf spring 60 is secured at 6! to the bearing 50 and acts normally to hold the lever arm 54 in the position shown in full lines in Fig. 2, but this spring 60 is yieldable to permit the arm 54 and roll 57 to pivot around stud 53 to the dotted line position shown in Fig. 2. Extending upwardly from the bearing, 50 is an arm 62 the upper end of which is connected to a cable: 63 the forward end of which is connected as at. 64 to the thread holder arm 32.

Secured to the top shaft I is a rotary cam or actuator member 65 having a .low area 66, an incline 67, and a decline 68. The cam is relatively thin so that it will fit between lever arm strip 56 and flange 59, but under ordinary running conditions the cam will rotate without en gaging the roll and the lever arm 54 and therefore the thread holder will remain at rest. A tension return spring 70 having one end 1] connected to the magazine and the other end 12 connected to the arm 32 tends normally to hold the latter forwardly against the forward stop screw 40 on diverging arm 38 to hold the thread holder member in its normal forward position, or to the left as shown in Fig. 1, but this spring will yield to permit the thread holder H to move rearwardly.

A controller means for the operating means, designated generally at C, operatively connects the lever arm 54 and the setting shaft ii. Included in this mechanism C is an arm 75 fixed with respect to shaft l7 and having a finger l6 adjustably connected thereto by bolts 11. The lower end of the finger 16 is below shaft l1 and has a stud 18 on which is pivoted a head .19 secured to the core 80 of a push-pull flexible wire designated at 8!. This wire has a coiled spring shield 82 which is held in fixed position on the magazine by a clamp 83. The shield is held by a second clamp 84 mounted on the. stop Y36 and by a third clamp 86 fixed with respect to the loom frame, see, Fig. 2. The core 80 has a second head .87 to which is connected one end of a tension energy storing spring 878 the other end of which is connected at 89 to the lever arm 54. Spring 88 is normally unstressed.

In operation, the parts will be in the normal position .shown in Figs. 1 and and in the full line position shown in Fig. 2. When a weft replenishing operation of the loom is indicated shaft I! will rock to its set position and move finger 16, stud l8 and head 19 to the dotted line position shown in Fig. 5, thereby moving the core 80 to the right as viewed in Fig. .5 to cause head 81 to exert a pull on spring '88. As already mentioned this rocking of shaft I! will occur when the lay is in the rear part of its reciprocation between its top and bottom center positions and at a time which is too early to start the back and forth motion of the thread holder. At this time the roll 51 will not be in register with the low area 66 of the .cam but will register with a part of the cam on its side corresponding to a high area of the cam periphery. spring- 88 is pulled, therefore, the flange 59 will engage the side of the cam and spring 86 will be expanded and have energy stored in it.

As the cam continues to turn the low area 66 will arrive in lateral register with the roll 51 at approximately the time the lay is on its bottom center position, and at this time spring 88, which when expanded exerts a stronger force than does spring 60, will contract to move lever arm 54 so that roll 5'! will align with the cam. The period of backward movement of the thread holder begins at this time, and as the cam continues to turn its incline will engage the roll 51 between flange 59 and lever part 56 to rock the lever L clockwise, Fig. 9, to move arm 62 rearwardly, or to the right as viewed in Fig. 9. Rearward movement of the thread holder will be completed at or about the time the lay reaches its top center position. When the lay reaches front center the shuttle will be replenished by a reserve bobbin and the setting shaft if will return to its normal position. The pull on spring 88 will therefore be slackened and leaf spring 60 will tend to return lever arm 54 to the full line position shown in Fig. 2, but the flange 59 will engage a side of the cam to hold the roll aligned with the cam.

By the time the thread holder has reached its rearmost position, see the dotted line position shown in Fig. 9, the freshly replenished shuttle will be picked by the picking mechanism P. The thread holder will now be in its rear position, see full lines Fig. 10, so that the thread WI extending from the thread holder to the replenished shuttle will be favorably placed for self-threading of the shuttle when the latter is picked. The lay will continue to move rearwardly as the shuttle moves along it and these parts will be as shown in dotted lines, Fig. 10, at some later time in the operation of the loom.

As the cam continues to turn the roll will move down the decline of the cam and enable spring 10 under control of the cam to return the thread holder to its front position, at which time the thread WI will be moved under the center filling stop motion fork F when the lay is at or near bottom center, and preferably while the shuttle is still in flight. By this time low area 66 will be under roll 58 and leaf spring 69 will be able to return lever arm 54 to its normal position shown in full lines, Fig. 2.

From the foregoing it will be seen that the invention, sets forth simple means by which a driving shaft of the loom can be utilized to move the thread holder rearwardly to facilitate threading of a freshly replenished shuttle and then forwardly to move the thread under the fork of the filling stop motion. The operation is initiated by rocking of the setting shaft to itsv transfer or set position, and a resilient element, such as spring 88., in which energy derived from the setting shaft can be stored permits a delay in the time at which rocking of the cam lever L is begun by the cam until the back and forth movements of the thread holder can be completed in a one-cycle period. The setting shaft remains in its set position long enough to enable the incline on the cam to begin the up motion of roll 5? and by the time the setting shaft is returned to its normal position the flange 59 will hold the roll 51 aligned with the periphery of the cam until the low area of the camagain arrives under the roll. This feature of continued rocking of lever L after resetting of shaft I! is not limited to a one-pick cycle of operation of the loom shaft. The spring 88 is stronger than spring 60 and overpowers it when the low area of the cam arrives in register with the roll. The spring 70 which moves the thread holder forwardly from its rear position also acts to hold the roll against the periphery of the cam. Return of the thread holder to its front position by spring H1 is controlled by the cam. While the setting shaft has been described herein as returning to its normal position when the lay is on front center, certain features of the invention are not necessarily restricted to this time of resetting of the setting shaft.

Having now particularly described and ascertained the nature of the invention and in what manner the same is to be performed, what is claimed is:

1. In a weft replenishing loom having a center filling stop motion fork and a self-threading shuttle which on a replenishing operation of the loom is replenished by a bobbin from which a thread extends, a shaft which rotates during loom operation, an actuator member secured to and turning with said shaft, a thread holder member to which the thread is attached mounted to be located either in front or back position in the loom, operator means for the thread holder member having a part thereof permanently connected in operative relation with respect to one of said members and having another part thereof capable of operative relation with the other member but normally inoperatively related to said other member, a setting shaft which moves from the normal position thereof to set position preparatory to said replenishing operation, and means controlled by said setting shaft operative incident to movement of the latter to the set position thereof to effect operative relation of said other part of said operator means with the other member, the actuator member being so constructed that it thereupon cooperates with said operator means to effect movement of the thread holder to the back position thereof to place said thread favorably for self-threading of the shuttle when the latter is picked subsequent to replenishment thereof, and means thereafter effective to move the thread holder forwardly to move the thread under said filling stop motion fork.

2. In a weft replenishing loom having a center filling stop motion fork and a self-threading shuttle which on a weft replenishing operation of a loom is replenished by a bobbin from which a thread extends, a thread holder to which the thread is attached mounted for back and forth motion in the loom, a shaft which rotates during loom operation, actuator means rotated by the shaft, a setting shaft which moves from the normal position thereof to set position preparatory to said replenishing operation, operator means controlled by the setting shaft effective due to movement of the setting shaft to the set position thereof to cause the actuator means in cooperation with the operator means to move the thread holder rearwardly to position said thread favorably for self-threading of the shuttle when the latter is picked subsequent to replenishment thereof, and means thereafter effective to move the thread holder forwardly to locate the thread under said filling fork.

3. In thread control mechanism for a weft replenishing loom having a lay provided with a center filling stop motion fork and having a selfthreading shuttle which on a weft replenishing operation of the loom is replenished by a bobbin from which a thread extends, a shaft moving the lay successively through front, top, back and bottom center positions each beat of the loom, means to pick the shuttle subsequent to said replenishing operation when the lay is approximately on the next top center position thereof, a thread holder to which the thread is attached capable of occupying either front or back positions in the loom, a rotary actuator driven by said shaft, a setting shaft moving from the normal position thereof to set position thereof preparatory to said replenishing operation while the lay is between its top and bottom center positions on the beat of the loom in which said replenishing operation occurs, means controlled by said setting shaft and operated by said actuator efiective due to movement of the setting shaft to the set position thereof to begin movement of the thread holder rearwardly when the lay is approximately on the bottom center position thereof and complete said movement of the thread holder when the lay is approximately on the top center position thereof to move the thread to a rear position favorable for self-threading of the shuttle when the latter is picked subsequent to said replenishing operation, and means thereafter efiective by the time the lay next reaches approximately the bottom center position thereof to move the thread holder forwardly to move the thread forwardly under said filling fork.

4. In thread control mechanism for a weft replenishing loom having a lay provided with a center filling stop motion fork and having a self-threading shuttle which on a weft replenishing operation of the loom when the lay is approximately on the front center position thereof is replenished by a bobbin from which a thread extends, a driving shaft which moves the lay successively through front, top, back and bottom center positions each beat of the loom, a cam secured to and rotating with the shaft once each beat of the loom, means to pick the shuttle subsequent to said replenishing operation when the lay is next on approximately the top center position thereof, a thread holder to which said thread is attached capable of being either in front or back position in the loom, a setting shaft moving from the normal position thereof to set position thereof preparatory to said replenishing operation when the lay is between the top and bottom center positions thereof on the beat of the loom when said replenishing operation occurs, operator means connected to the thread holder normally out of operative relation relative to said cam, and means controlled by said setting shaft effective incident to movement of the latter to the set position thereof to move said operator means into operative relation with respect to the cam when the lay is substantially on the bottom center position thereof on the beat of the loom in which said replenishing operation occurs, said cam thereafter effective in cooperation with the operator means to move the thread holder to the back position thereof to locate said I thread favorably for self-threading of the shuttle when the latter is picked subsequent to said replenishing operation, and means thereafter effective to return the thread holder to the front position thereof by the time the lay next reaches substantially the bottom center position thereof to move the thread under the fork, and means thereupon effective to move the operator means to a position out of operative relation with respect to the cam.

5. The structurelset forth in claim 4 wherein said means controlled "by the setting shaft includes a resilient element in which energy derived from the setting shaft is stored between the time the setting shaft moves to the set position thereof and the next following bottom center position of the lay, said element due to the energy stored therein being effective to move the operator means into operating position relative to said cam.

6. The structure set forth in claim 4 wherein means operating upon return of the thread holder to the front position thereof moves the operator means to a position out of operative relation with respect to the cam.

7. In thread control mechanism for a weft replenishing loom having a lay provided with a center filling stop motion fork and having a selfthreading shuttle which on a weft replenishing operation of the loom is replenished by a bobbin from which a thread extends, a shaft which moves the lay successively to front, top, back and bottom center positions each beat of the loom, means to pick the replenished shuttle when the lay is substantially on the top center position thereof subsequent to said replenishing operation, a thread holder to which said thread is attached mounted to be located either in front or back position in the loom, a cam having high and low areas driven by said shaft, operator means connected to the thread holder normally out of operative relation with respect to said cam, a setting shaft which preparatory to said replenishing operation moves from the normal position thereof to set position when the lay is between the top and bottom center positions thereof on the beat of the loom on which the replenishing operation occurs, said setting shaft returning to the normal position thereof subsequent to arrival of the lay at the bottom center position thereof on the beat of the loom in which said replenishing operation occurs and prior to picking of the replenished shuttle, and means controlled by the setting shaft operative incident to movement of the setting shaft to the set position thereof to move the operator means over the low area of the cam when the loom is substantially on the bottom center position thereof, whereupon said cam causes the operator means to move the thread holder to the back position thereof to locate said thread favorably for self-threading of the replenished shuttle when the latter is picked subsequent to return of said setting shaft to the normal position thereof, and resilient means effecting forward movement of the thread holder subsequent to picking of the replenished shuttle to move said thread under said filling fork.

8. In thread control mechanism for a weft replenishing loom having a lay provided with a center filling stop motion fork and having a selfthreading shuttle which on a weft replenishing operation of the loom is replenished by a bobbin from which a thread extends, a shaft turning to move the lay successively through front, top, back and bottom center positions each beat of the loorn, means to pick the shuttle subsequent to said replenishing operation when the lay is next on approximately the top center position thereof, a cam having high and low areas rotated by said shaft, a thread holder to which the thread is attached mounted to be located either in front or back position in the loom, operator means connected to the thread holder normally inop- 10 eratively related with respect to the cam, a set-. ting Shaft moving from the normal position thereof to set position thereof when the lay is between the top and bottom center positions thereof on the beat of the loom in which said weft replenishing operation occurs, said setting shaft returning to the normal position thereof when the lay is substantially on the front center position thereof during said weft replenishing operation, means controlled bythe setting shaft effective incident to movement of the latter to the set position thereof to move the operator means over said low area and into operative relation with respect to said cam, the latter thereupon causing the operator means during a period beginning prior to return of the setting shaft to the normal position thereof and continuing after said setting shaft returns to its normal position to move the thread holder to the back position thereof to place said thread favorably for self-threading of the shuttle when the latter is picked subsequent to said replenishing operation, means maintaining the operator means in operative relation with respect to said cam subsequent to return of the setting shaft to the normal position thereof, and means effective subsequent to picking of the replenished shuttle to effect forward movement of the thread holder to move the thread under said filling fork.

9. In thread control mechanism for a weft replenishing loom having a center filling stop motion and a self-threading shuttle which on a weft replenishing operation of the loom is replenished by a reserve bobbin from which a thread extends, the replenishing operation occurring when the lay is on the front center posi tion thereof and the loom thereafter effecting picking of the shuttle when the lay is at or near its top center position, a thread holder to which the thread is attached, means mounting the thread holder for movement either to back or forward position, return means normally holding the thread holder in forward position, a setting shaft rocking from the normal position thereof to set position when the lay is in rearward position prior to said replenishing operation, a cam rotating once for each one pick cycle of the loom having high and low areas, a cam lever mounted for angular motion on the loom having an arm operatively connected to the thread holder and having another arm normally inoperatively related to the cam but movable into operative position relative to said cam, and a controller for said other arm including a resilient element connected to the setting shaft effective upon movement of the latter to the set position thereof to move said other arm laterally against a part of the cam corresponding to the high area thereof and store energy in said element, continued turning of the cam causing the low area thereof to register with said other arm, whereupon said element effects alignment of said other arm with the cam and the latter thereupon causes the cam lever to move the thread holder to the back position thereof to locate the thread favorably for self-threading of the replenished shuttle when the latter is picked, said return means being thereafter effective to move the thread holder forwardly subsequent to picking of the shuttle to effect movement of the thread under the filling stop motion fork.

1G. The thread control mechanism set forth in claim 9 wherein said return means acts through said one arm of the cam lever to hold said other arm against the cam while the high area of the latter engages said other arm. REFERENCES CITED 11. The thread control mechanism set forth in The following references are of record in the claim 9 wherein said other arm is plivoted on the fil f this patent: cam lever and a spring normally ho ds said other arm out of operative position relative to the cam UNITED STATES PATENTS and. said element is a second spring strong enough Number Name Date to overpower the first spring. 2,182,103 Wiget Dec. 5, 1939 2,531,176 Turner Nov. 21, 1950 RICHARD G. TURNER. 10 2,569,907 Turner Oct. 2, 1951 

